* Add enums and structures for GNU version information.
* Implement extraction of that information on a per-symbol basis (ELFObjectFile::getSymbolVersion).
* Implement a generic interface, GetELFSymbolVersion(), for getting the symbol version from the ObjectFile (hides the templating).
* Have llvm-readobj print out the version, when available.
* Add a test for the new feature: readobj-elf-versioning.test
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152436 91177308-0d34-0410-b5e6-96231b3b80d8
